No matter how many games in which troubled quarterback Ben Roethlisberger participates in 2010, the Pittsburgh Steelers know they have to play better, more resourceful defense than they did a year ago.

And they know that to do so, they will require the returns to health of strong safety Troy Polamalu and end Aaron Smith.

The two stalwarts appeared in only 10 games combined in 2009, Polamalu falling victim to a sprained left knee (which did not require surgery but was twice injured) and Smith to a torn right rotator cuff. Not surprisingly, Pittsburgh dropped to 9-7 and failed even to qualify for the playoffs after having won Super Bowl XLIII the previous season.

The good news? "Given all the stuff that happened," Polamalu said at last weekend's minicamp, "we still finished only one game out [of the playoffs]. So there's no big need to tear everything down and start all over. I mean, the nucleus is still here."

The better news? Polamalu and Smith appear to be healthy. Smith, one of the NFL's best and most underrated 3-4 ends, said: "I feel really good, and I've pretty much been cleared to do everything. … I want to make up for lost time. I'm not a very good sit-and-watch guy."

Smith and Polamalu are hardly the only veterans in the league being counted on to do more than man the remote control this season. As is the case in every campaign, there is a considerable group of veterans on whom teams are relying to return fully healed and play key roles in 2010.

For the purposes of this column, the comeback players are limited to those who missed at least eight games last season.

So while the recovery of New England slot receiver Wes Welker from a severe knee injury is critical to the Patriots, he is not listed here. Ditto for Carolina offensive tackle Jordan Gross, Panthers linebacker Thomas Davis, Minnesota middle linebacker E.J. Henderson, Green Bay cornerback Al Harris and Detroit tailback Kevin Smith, among others. The returns of those players, and more, are essential to their respective franchises; they just didn't meet the eight-game standard for consideration.

And although two-time Pro Bowl left tackle Jammal Brown of New Orleans qualified by not playing a single snap in '09, the Saints still won the Super Bowl with his replacement, Jermon Bushrod, performing pretty well.

Even without the above-named veterans, the assemblage of players whose returns are critical is lengthy and impressive.

Of course, that is typically the case, especially for those franchises that didn't make the playoffs. Few clubs, though, suffered the kind of double whammy that the Steelers experienced on defense. Make no mistake: The absence of Polamalu and Smith from the lineup made a significant difference for crafty coordinator Dick LeBeau and the way he developed game plans and orchestrated his defensive calls.

"The guys who filled in did fine," LeBeau said. "But when you're talking about [Smith and Polamalu], you're talking about some special people. They're game-changers."

Pittsburgh lost all seven games last season by seven points or fewer. Five of the defeats were by three points or fewer.

Worse, Pittsburgh either was tied or led in the fourth quarter of six of the losses.

The Steelers' statistical drop-off wasn't great -- they fell from No. 1 in the league in 2008 to fifth in overall defense in 2009 -- but the pass defense rated No. 16 and Pittsburgh was 12th in the NFL in points surrendered. And the team seemed to lack a killer instinct, the ability to close out games defensively, long the strength of Pittsburgh defenses.

Said free safety Ryan Clark: "We just couldn't make the key stop when we needed it; we couldn't get ourselves off the field."

The hope is that by getting Polamalu and Smith out of the trainer's room and back onto the field, that will change. Smith, 34 and a one-time Pro Bowl performer, is a terrific two-way player, stout against the run and still able to provide some upfield push on early downs. The 29-year-old Polamalu is one of the game's premier defensive playmakers, a five-time Pro Bowl performer, and the uniquely versatile player around whom LeBeau conjures up many of his exotic schemes.

At last week's minicamp, Polamalu, who had three interceptions in 2009 despite playing in only five games, discussed the need to create chemistry on the field. A good start toward that goal: Barring setbacks, the Steelers should have two of their key elements back on defense in 2010.